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Calling all experts, can you help?

Grade 3/4 are calling for help! We have started our personal inquiries about how the earth’s surface changes. We have posted our rich questions below, if you can help us answer a question could you please leave a comment explaining what you know?

Dear Mrs Boyhan and Class,
I love your idea of asking experts for help on your interesting questions. I don’t have a lot of personal knowledge about these things so I have ReTweeted your request to some Geography teachers who should be experts. I hope they can get back to you with some answers.
All the best
Mrs Coffa

Tsunamis are caused by disturbances of the seafloor that cause a large volume of water to be displaced, usually as a result of earthquakes (like the 2004 Indian Ocean or 2011 Japan tsunamis) or sometimes by large landslides (like the Lituya Bay tsunami in Alaska in 1958). They can occur in the sea or even in large lakes, and they are so destructive for a couple of reasons:

1. They are difficult to predict and difficult to identify in the wider ocean; although earthquakes and landslides can be detected, they are difficult to predict, and not all earthquakes and landslides cause tsunamis. It is also difficult to identify tsunamis out at sea; the tsunami wave only grows in height when it nears land, and may not be identifiable away from the coastline. All of this means that preparing effective tsunami defences is very difficult.

2. The size and speed of a tsunami is another reason that they are so destructive. Out at sea a tsunami can travel at speeds of 800 km per hour, although this decreases to a (still fast) 80 km per hour as they get closer to land. They also increase in size as the water in the tsunami is compressed near coastlines by the shallowing of the seabed.

This combination of speed and wave height means that tsunamis essentially become a very high wall of water that travels at high speed, smashing anything in coastal areas that is in its way and potentially moving significant distances inland. The unpredictability of these events also means they are difficult to defend against, and people living in coastal areas may have little or no warning of an incoming tsunami, meaning they may not be able to escape to higher ground above the tsunami wave height. The final type of destruction associated with tsunami events is the movement of water away from the land after the tsunami – the water brought inland by the event will also move back to the sea or lake, carrying debris with it and potentially causing more destruction after the initial impact of the wave.

Tornadoes are rapidly rotating columns of air which extend from the base of a thunderstorm to the ground. The strength of tornadoes is measured by how much damage they cause using the “Enhanced Fujita (EF) Scale”. The weakest tornadoes (rated EF0) may cause almost no damage; the strongest (rated EF5) can completely destroy buildings and throw cars and trucks hundreds of meters.

Most tornadoes form underneath powerful thunderstorms called “supercells”. These storms themselves rotate, as can often be seen in time-lapse footage of them (https://vimeo.com/95819708).

To see how the rotation forms, lie a pencil on the palm of one hand, then place the palm of your other hand on top and move it forward: the pencil will rotate. The same thing happens in the atmosphere when wind speed increases with height above the ground. The resulting rotating “tubes” of air are sucked into the thunderstorm and tilted so that they point upwards. The strong rising motion in the storm then stretches them so that they become taller and skinnier. This makes the air spin even faster, just like an ice skater spins faster when she pulls her arms in.

If the spinning air can reach all the way to the ground then a tornado forms. However, scientists are still trying to understand exactly how this happens.

Tectonic plates are sections of the earth’s crust. The molten rock under the crust is always hot and churning around, so the crust of the earth is also constantly moving as well, a bit like the way skin forms on the top of simmering hot milk.

Unlike milk, this happens very slowly – the tectonic plates shift 2.5 to 7 centimetres per year, or about 25 to 50 kilometres over one million years.

In some places the tectonic plates move away from each other forming ridges pushing the plates apart.

In other places, the continents crash into each other, which can cause earthquakes, mountains and volcanoes.

Being here in Australia makes us a bit safer from these sort of problems – Australia is in the middle of a large tectonic plate, not near the edge, se we are far away from the ‘collision sites’. We are moving north at 6-7 cm a year; and eventually Australia will bump into the Asian plate.

Hi 3/4LB,
I have seen some of the things that you have done and I enjoyed reading them. My favorite was your personal inquiry’s. I found all of your topics and questions very interesting. I found these questions especially interesting:
– How and why do tectonic plates moves?
– Why do asteroids do so much damage?
– How do tsunamis occur?
– Why are tornadoes so destructive?

Hi 3/4LB,
Your personal inquiry questions are fabulous as well as your blog. I think I can answer Isabelle’s question, ‘How does a volcano erupt?’. A volcano starts to erupt when magma rises through the cracks of the earth’s crust. When the pressure is released, magma explodes to the surface and that causes a volcanic eruption.

I also think I can answer Georgia’s question, ‘What causes a tornado?’. The feirce spinning of a tornado is partly a result of the updrafts and downdrafts in the thunderstorm which is caused by unstable air.

It depends how powerful the tsunami is, if it is caused by an earthquake and the earthquake is 8.8 on the reicter scale the tsunami would be powerful but if it is just 1.0 it would be a small wave. Or say if it was caused by a meteor or a avalanche, it depends how big they are.